Yes, I was thinking of the built-in plugin. Fully charge the battery, set playback to repeat and start playing a long playlist or a big file and leave the player alone until there comes no sound out of the headphones anymore. I always use -40 db and a single mp3 with the size of about 120 MB.

I just made a benchmark with my 1900 mAh battery (the 'standard' high capacity battery size), and I reached 65 hours. So I think yours is mislabelled as 3000 but is in reality a 1900 mAh, this type of scam is very frequent (and I have yet to see an actual 3000 mAh battery for iPod).

That being said, the capacity doesn't go high enough for 1900 mAh, and yes it's totally accessory but I get that you'd like it to go this high

I think you just have to compile a build of Rockbox from the sources (on github), you'd be able to first edit the BATTERY_CAPACITY_MAX variable in the file /firmware/export/config/ipodvideo.h

I just made a benchmark with my 1900 mAh battery (the 'standard' high capacity battery size), and I reached 65 hours. So I think yours is mislabelled as 3000 but is in reality a 1900 mAh, this type of scam is very frequent (and I have yet to see an actual 3000 mAh battery for iPod).

That being said, the capacity doesn't go high enough for 1900 mAh, and yes it's totally accessory but I get that you'd like it to go this high

I think you just have to compile a build of Rockbox from the sources (on github), you'd be able to first edit the BATTERY_CAPACITY_MAX variable in the file /firmware/export/config/ipodvideo.h

I think Tarkan had it right in his analysis that simply considered the physical volume of each of those batteries (2000,1900,3000) and concluded they were probably in reality about 1700,1700 and 1800 respectively. The 3000mah one is slightly larger volume than the others, and personally my suspicion is they are all made much the same way out of much the same materials in the same Chinese factory, so size is likely the only factor.

I still feel it would be technically possible to fit a still larger battery in a thick ipod, but it would have to be an irregular shape (to use all the available space), and I don't know if that is possible with batteries, and I'm sure would be more expensive to manufacture if it were.

Is it not possible to set the battery capacity in the fixed.cfg file? You can't set it high enough via the menu, but the fixed.cfg file seems to allow any number. Not that it matters in the slightest as the battery indicator is wildly inaccurate anyway.

Also, since that samsung exploding phone scandal, I've become quite nervous about all the devices I have with largish lipo batteries. I did have one (of many) 3000mah and one 2000mah swell up, though not enough to pop open the ipod.